The present invention relates to a machine for sealing variable-height parallelepipedal cartons.
In the Italian Pat. No. 946715 and in the U.S. Pat. No. 4,060,442, both in the name of the same Applicant, there are disclosed sealing machines of the kind including a carton support and advancement base, an upper sealing head superimposed to said support base in a vertically displaceable manner and, usually, a lower sealing head included in said support base.
In order to be able to adjust automatically the vertical position of the upper sealing head to the variable height of the cartons to be sealed, such machines are arranged so that on the inlet end of the upper sealing head, which is normally urged by gravity to a minimum-height position, there is mounted a sensor formed by a sensing lever which can be engaged by the front wall of the incoming cartons. Through a suitable pneumatic device the above cited sensing lever is able, when engaged, to cause the upper sealing head to rise up to a sufficient height for the disengagement of the sensing lever, that is to such a height as to allow the manual or mechanical introduction of the cartons between the support base and the upper sealing head. As a result of the disengagement of the sensing lever, the upper sealing lever stops its rising motion and rests by gravity on the top of the carton, applying therein the closing means, for example a strip of adhesive tape, as the carton is manually or mechanically advanced along the support base.
Such known machines have the only disadvantage that the sensing lever is mounted on the upper sealing head, so that during working it is maintained by the same weight of the sealing head in close proximity to the closed upper flaps of the cartons. It has been possible to verify experimentally that, due to unavoidable flap forming and/or positioning irregularities, this may cause unwanted actuations of the sensing lever and, thus, irregular operations of the sealing head. As a final consequence, the cartons sometimes go out of the machine without being carefully sealed.
Object of the present invention is to realize a sealing machine with automatic adjustment to different height cartons, in which the above said disadvantage does not occur.
According to the invention, such an object is attained by means of a machine, comprising a carton support and advancement base, an upper sealing head superimposed to said support base in a vertically displaceable manner from a minimum-height position, and sensing means engageable by the carton body to cause said sealing head to rise automatically from said minimum-height position to a sufficient height to allow the introduction of the carton between said support base and said sealing head, characterized in that said sensing means are mounted on said support base in such a position as to be engageable by the bottom of the carton.
Otherwise stated, the machine according to the invention therefore provides for the mounting of sensing means no longer on the vertically displaceable sealing head, but on the same carton support base, so that it is the carton bottom which engages said sensing means to cause the sealing head to rise up to the desired height. The result is that the operation of the sealing head is no longer influenced by the more or less regular status of the carton top, while the carton bottom, made regular by the weight of the packed products, in turn causes a correct engagement of the sensing means and, therefore, a constant and regular operation of the machine.
Preferably, said sensing means are constituted by a lever having two sequentially attainable positions, in one of which said rising of the head is caused and in the other of which, subsequently to the introduction of the carton between the support base and the sealing head, the sealing head is caused to go down again on the carton top.
Otherwise, it may be foreseen to use two levers arranged in succession along the carton advancing path.
The features of the present invention will be made more apparent by the following detailed description of non-limiting example in the accompanying drawings. in which: